Foam seat sensor

ABSTRACT

A planar, low profile switch assembly at each occupant position of a foam vehicle seat construction comprises upper and lower spaced, flexible conductive metal strips with a foam strip interposed between and separating the metal strips. Primary lances partially struck from the upper strip normally lie in the same plane as the upper strip proper but are flexed by seat occupation, the primary lances deflecting through openings in the foam strip to make contact with the lower metal strip. A plurality of longitudinally spaced secondary lances are carried at the free end of the primary lance for contact wiping and arc prevention, respectively.

United States Patent 1 Tiazkun et al.

[ 1 July 3l, 1973 FOAM SEAT SENSOR [75] Inventors: Michael GeorgeTiazltun, Lykens',

Winfield Warren Loose, Linglestown, both of Pa.

[73] Assignee: AMP Incorporated, l-larrisbug, Pa.

221 Filed: May 1, 1972' 21 Appl. No; 249,114

[52] US. Cl 200/85 A, 340/272, 180/102 [51] Int. Cl. 1101b 3102 [58]Field of Search 200/85 R, 85 A, 86; '307/10 SB; 180/102; 340/52 E, 272

(56] References Cited I UNITED STATES PATENTS 11/1970 Butler 307/10Primary Examiner-Herman J. Hohauser Attorney-William J. Keating,Frederick W. Raring etal.

ABSTRACT A planar, low profile switch assembly at each occupant positionof a foam vehicle seat construction comprises upper and. lower spaced,flexible conductive metal strips with a foam strip interposed betweenand separating the metal strips. Primary lances partially struckfromethe upper strip normally lie intthe same plane as 7 Claims, 13Drawing Figures I PAIENIEUJ 1 I 3.749.866

sum 2 or 4 PAIENIEU JUL 3 1191s SHEET 3 OF 4 PATENIEBJULaI new I sum uor 4 FOAM SEAT SENSOR BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to vehicle seat occupant sensingswitches, and more particularly to a planar, low

profile switch assembly, particularly useful in conjunc tion with foamseat constructions.

2. Description of the Prior Art I I In the development of automotivevehicles, seat constructions employing multiple coil springs forresiliency have long'been employed. In an effort to provide more Nsponsive to the sensing of the occupancy of the seat,

have been employed, in conjunction with other switches responsive toproper coupling of seat belts, to either inform the driver and the otheroccupants of the vehicle that proper safety procedures have beenfollowed or, in some case, have been employed to actually preventvehicle operation in the absence of completion of buckling of the seatbelts. In an effort to insure that only those seat belts for eachoccupant position actually used have been coupled, switches have beenincorporated in the seat constructions at each possible occupantlocation or position to sense the occupant, with the switches beingappropriately connected electrically within the electrical safetysystem. One attempt at providing a localized indication of occupancyinvolves a planar switch assembly achieved by placing a perforated, openfoam pad between two sheets or strips vof conductive metal such ascopper which, in turn, have facing dimples or protrusions aligned withthe perforations or holes in the foam such that during occupancy thefoam collapses, and the dimples make contact. While such seat sensorswitches act to some degree of satisfaction, there are inherentdifficulties and problems with respect to such structuresfSince pointcontact is made between the dimples, there is no scrubbing or cleaningaction, that is, there is no relative movement between the surfaces incontact. Without a wiping action, arcing occurs which builds upoxidation around the area of contact which then leads to resistance atthat point, between the switch contact areas. Further, the resiliency ofthe foam pad is required to return the metal sheets to non-contactposition and, depending upon the extent of occupancy or the weight ofthe occupant, a compressive set may occur, which may be to such a degreeas to indicate continued occupancy although the occupant has left thevehicle. Further, seat constructionsof this type have involved sensorspositioned on the two outside positions and a center posi-' tion, as inthe rear seat of'aconventional passenger sedan, for instance. Occupantsof the two outside" seat cationscreate during the depression of the foampor tion of the seat, tension across theisurface of the upper sheetwhich-tends to pull-it into contact with the lower conductive sheet atthe center of the seat so as to close even though no occupant is sittingin the centerposition. In such a case, in theabsenceof the occupant, thefailure to further connect the seat belt corresponding to the centeroccupancy position of that particular seat renders a false indicationand may prevent operation of the vehicle although all occupants in thevehicle have properly coupled their seat belts.'

SUMMARY OF THE INVENTION The present invention is directed to animprovedplanar, low profile switch assembly operable by distortion I dueto a human body-positioned upon the same, the assembly comprising anupper flexible, conductive metal strip, spaced from a similar lowerflexible conductive metal strip, by a foam member interposed between thestrips and tending to maintain the strips in spaced,noncontactpositionin the absence of the human body. At-

"11cm one 'lanceis partially struck from the upper strip and normallylies in the same plane as the upper strip proper, but is displaceabletowards the other strip during forcible depressed distortion of theassembly. .The foam member includes a recess surrounding the primarylance which permits deflection of the lance withinv the foam memberopening and into contact with'the lower metal strip.

Preferably, the primary lance includes two secondary lances'which arelongitudinally spaced from each other and adjacent the free end of theprimary lance, the primary and secondary lances being partially struckfrom the upper strip and from the primary lance respectively in adirection such that the outboard secondary lance effects a wiping actionin the area of contact with the lower strip by a slight extensionandretraction of the.

primary lance whilethe inboard secondary lance maintains contact withthe lower metal strip upon possible bouncing of the first secondarylance to prevent arcing between the metal strips at the contactinterface. v,

. In one embodiment, a solid second foam strip over.,

lies theupper metal strip, whereby compression of they switchassembly bybody contact causes a localized portion of the second foam stripcorresponding to the opening in the upper strip defined by the primarylance to depress the primary lance into contact with the lower metalstrip, but upon release thereof, the bias of the primary lance forcesthe localized deformed portion of the second foam member to returnthrough the opening and returns theprimary lance tocoplanar positionwith respect to the upper metal strip proper. Preferably,each planar lowprofile switch assembly is carried within recesses within afoam padspanning a vehicle seat construction with the number of recesses cor-'responding to the possible seat occupancy positions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view ofanautornotive vehicle seat incorporating a plurality of foam seat sensorswitches of the present invention, in one form, at each possible seatoccupancy position.

FIG. 2 is a perspective view of one embodiment ofa foam seat sensorswitch employed in the vehicle seat constructionof FIG. 1. I t 1" FIG. 3is an exploded, perspective view of the seat switch of FIG. 2. I

, FIG. 4 is a sectional view of the seat switch illustrated,

.inFlGS'.2and3. -1 FIG. 5 is a diagrammatic side view of th'e'seatillus; trated in FIG. 1, during occupancy, with thedotted line FIG. 11is a diagrammatic view of a seat incorporating the switch of FIGS. 9 and10, during occupancy, the dotted line position indicating the positionof the switch components when the seat position is unoccupied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The switch assemblies in the,--multiple embodiment forms as shown, have application to conventionalautomotive vehicles, particularly in conjunction with seatsincorporating a foam pad as a resilient support member with or withoutconventional coil springs. Reference to FIG. 1 illustrates a vehicleseat construction 10 which may, for instance, comprise the rear seat ofan automobile sedan in which case there is provided three passengeroccupant positions, two at each side as indicated generally at A and Cand a center occupancyposition indicated generally at B. In thatrespect, the seat is equipped with a plurality of seat belts includingbelt sections 12 for the outside occupants which couple to extendablebelt sections 14 carried by reel 16 oh each side of the seat, the centeroccupant at position-B making use of belt section 18 which couples to asecond section 20. Coupling completes an electrical circuit (not shown)indicative of proper fastening of the seat belts for each passengersection. The seat 10 itself is rectangular in form and the upper half ofwhich comprises a foam pad which is recessed to receive individual,planar low profile seat sensor switches or assemblies 22 at eachoccupant position, A, B and C. It is preferred that each seat sensorswitch 22 cooperate with respective seat belt sections to indicate boththe occupancy of the seat portion by an occupant, and the me-.

chanical coupling of the belt halves or sections prior to permittingengine ignition or indicating by an appropriate light or buzzer thecompliance with the safety requirements, consisting in this case ofcoupling of the belt sections about the occupant.

Each of the seat sensor switches 22 in the embodiment employed in FIG.1, is illustrated further in perspective in FIG. 2 and in an explodedperspective view in FIG. 3. Upper and lower mylar film 24 and 26 areultrasonically welded together at weld points 28 to insure properplacement of electrical leads 30, the mylar film sheets 24 and 26 beinggenerally rectangular in form and carrying aligned apertures 32permitting the switch assemblies tobe maintained in proper positionwithin recesses (not shown) within the foam pad overlying the top ofseat 10. In FIG. 3, the mylar top and bottom sheets 24 and 26 areomitted for clarity, the upper mylar sheet 24 overlying a solid foamsheet or strip 34 which is approximately one-eighth of an inch inthickness and formed of conventional open foam, plastic material whichis an electrical insulator. In fact, the foam strip 34 may be of theidentical material to that which forms the foam pad of the seat 10. Thefoam strip 34, overlies an active metal conductor strip 36 whichisattached to one of the electrical leads 30 by a suitable connector 38strip 36 constituting in this case an active conductor of the switchassembly. Lying beneath the active conductor strip 36 and separating theactive conductor strip 36 from the solid passive metal conductor strip38, is a second open foam, plastic sheet or strip 40 of generally thesame rectangular configuration to sheet 34,'but in this case beingprovided with a rectangular opening 42 running longitudinally throughthe center of the same, generally in line with the active conductor36.The active conductor strip 36 is slightly I wider than the opening 42 offoam strip 40. A series of integral, flexible primary lances 44 arestruck partially from the active conductor strip 36. In the embodimentof FIG. 3, E-shaped openings 46 are formed within the active conductorstrip to define the paired lances 44 at three longitudinally spacedlocations. Active conductor 36, the opening 42 and underlying passiveconductor 50 extend generally in longitudinal alignment with the body ofthe occupant, the switch assembly 22 being less than the width of anaverage occupant. Thus, the number of primary lances 44 which arecarried by the active conductor are esssentially the number sufficientto insure that at least one of the lances makes electrical contact withthe underlying passive conductor which nor-' mally is spaced from thesame by the thickness of the interspersed foam pad 40. Terminal48connects the passive conductor strip 50 to the other electrical lead30 such that the flexure of any one of the primary lances downwardlythrough opening 42 and into contact with the upper surface of thepassive conductor completes an electrical circuit between the leads 30and is indicative of occupancy of the vehicle seat position or location.While the mylar sheets or films 24 and 26 are not shown in the explodedview of FIG. 3, the passive conductor may be bonded to the bottom mylarstrip 26 to facilitate properpositioning or assembly of the switchcomponents. The function of the mylar film or strip 26 is toelectrically isolate the passive conductor 38 with the exception of theprimary lances 44 carried by the active conductor which make contactwith the passive conductor through opening 42 of the interspersed foamstrip 40.

Reference to FIGS. 4-8 show in detail, the construction of each switchassembly 22 and its mode of operation. I

As more clearly seen in FIGS. 6, 7, 8a, 8b and 8c, each of the primarylances 44 is provided with first and second, secondary'lances 52 and 54these short lances being relatively rigid and struck from the center ofthe primary lancesSecondary lance 52 lies adjacent the end 56 of theprimary lance, while secondary lance 54 is spaced slightly inboard ofthe same. The secondary lances 52 and 54 depend downwardly, that is,they are actually bent with respect to the plane of the activeconductor, while in theunflexed position, the primary lances 44 are inline therewith. The secondary lances 52 and 54 are inclined in the samedirection as the primary lances 44, towards end 56 of the primary lance.

Each secondary lance $2 and 54 for eah primary lance 44 perfonns aparticular function during switching and, effectively, each secondarylance forms a lance within a lance on the active conductor. Whenpressure is applied to the upper, solid foam strip 34, at locationsdefined by the E-shaped openings 46 within the active conductor 36,localized portions of the solid foam strip- 34 protrude through, theopenings forcing the primary lances 44 downward, the primary lances 44being essentially cantilever mounted such that ordinarily the outboardsecondary lance 52 makes initial contact with the passive conductorstrip 38. The contact between permit fixing of the assembly in theproper position wipes first, in a forward direction a'crossthe uppersurface of the passive conductor strip 38 and then in a reversedirection, that is, the primary lance overrides during the bounce, theinboard secondary lance 54 then may make contact with the same passiveconductor strip 38, in the event of extra pressure, thus relieving thepressure on the outboard secondary lance 52. Since the inboard secondarylance 54 is in contact with the passive conductor strip 38, there willbe no arcing between the outboard secondary lance 52 and the passiveconductor strip 38, due to the creation of a momentary gap between theseelements. Further, if only a single secondary lance is employedtocontact the lower electrode or passive conductor strip 38 initiallyeach time the switch completes the circuit, it may deteriorate becauseof arcing over a period of time. Normally, there is no danger, sinceduring continued occupancy, the switch is relatively static. The purposeof the parallel switches formed by each of the primary lances'44 is toinsure that contact will be completed between the active conductor strip36 and the passive conductor strip 28 at at least one primary lancelocation. Reference to FIG. 5 illustrates the fact that where arelatively thick foam pad constitutes the major portion of the seat,depression by an occupant U is essentially at right angles to the planeof the seat and the switch assembly 22 merely shifts from the dottedline position shown to'a full line position and is retained generally ina planar shape rather than shifting to an arcuate or curvedconfiguration. Further, reference to FIG. 7 indicates how localizedportions of the upper foam strip 34 move into the E-shaped openings 46and actually protrude well below the plane of the upper surface of thelower foam strip 40. 1

The embodiment ofFlGS. 1-8c is employed, in general, in a foam vehicleseat construction in which the resiliency of the seat is providedessentially by a single relatively thick pad of foam materialwhichcovers the top of the seat exclusive of the seat back. However, thepresent invention has application to seat constructions in which acombination of a foam pad and springs are employed to provide resilientsupport for the occupants. Reference to FIGS. 9, 10 and 11 illustratesan alternate embodiment of the seat sensor switch which is essentiallycharacterized by a lack of an outer foam sheet and wherein deflection ofthe primary lance at each location occurs, not as a result of localizeddefor mation to the foam overlying the upper metal conductor strip, butas a result of the curvature given to the planar low profile switches asa result of occupancy of the seat. The illustrated switch assembly isquite similar and, in many respects identical, to that of the priorillustrated embodiment, and like elements are given like primednumerical designations. In that respect, seat sensor switch or assembly22 comprises upper and lower mylar film sheets 24' and 26' ofrectangular configuration and acting to sandwich the remainingcomponents of the switch assembly with electrical leads 30' enteringfrom one end of the assembly, the mylar sheets 24f and 26' being alsoprovided with apertures 32' to within the seat construction 10'illustrated schematically in FIG. 11. The upper foam sheet is omitted inthis switch assembly and lying beneath the upper mylar film sheet 24' isin this case a pair of laterally spaced, longitudinally extending activemetal conductor strips 36' each of which carriesat one or morelocations, primary lances 44' which are struck out from the same, beingdefined by U-shaped opening 46', the primary lances being cantileversupported and integral with the active conductor sheets 36'. Lyingbeneath the active conductor strips 36', is an interposed open foam,plastic insulative sheet 40 which, in similar fashion to the priorembodiment, is provided with a rectangular opening 42' for eachconductor strip 36, being of a width less than the width of theconductor strips 36', but in excess of the width of the U-shapedopenings 46' within the active conductor strips 36'. The bottommylar'film strip 26 underlies the passive metal conductor strip 38 ateach active conductor strip location, the active and passive conductorstrips being generally of similar configuration, with the exception ofcourse that each passive conductor strip 38' is solid. The activeconductor strips 36' may be bonded to the bottom surface of the uppermylar strip 24 and the passive conductor strips 38' may be bonded atsimilar locations to the lower mylar film strip 26' with the foam strip'40 interposed between the same to normally prevent contact between theconductive strips. Electrical connections are made between lead wires 30and the respective conductor strips through appropriate terminals 32 and48', respectively. Terminal 32' further electrically connects the upperactive conductor strips 36, while terminal 48' performs the samefunction with respect to the underlying but electrically insulatedpassive conductor seat at a location of one of the switch assemblies 22"causes, in general, a fore to aft curvature, that is,.bending into aconcave configuration generally facing the back side of the occupant.

The movement of the planar switchassembly from a flat, straight or inline position, to a position of curvature effects switch closure. Sinceeach primry lance 44' is cantilever mounted, and since there isanabsence of foam tending to deflect the lance relative to the opening46' defining the same within the active conductor strip 36. upon convexcurvature to the complete switch assembly 22, each lance tends to moveto a position of tangency with respect to the conductive strip 36' fromwhich it is partially struck out. If sufficient curvature is given tothe sandwich, the foremost secondary lance 52 makes contact with theunderlying but spaced passive conductor strip 38', thus completing thecircuit between leads 30'. In this embodiment it is therefore acurvature mode which causes circuit completion. In like manner to theprior embodiment, any bounce experienced by the primary lance whichwould permit momentary opening between the forward or outboard secondarylance 52' and the underlying conductor strip 38. is prevented bysubsequent contact between the trailing or inboard secondary lance 52'.In the embodiment of FIGS. 9-11 during circuit completion, a slightextension and retraction of the primary lances 44' relative to therelatively fixed underlying passive conductor strip 38 occurs, theextension and retractionof the lance performing a wiping action in thearea of contact between the lances and strips 38', thus insuring a cleancontact area and circuit completion with minimum resistance. In bothembodiments, the leading or outboard secondary lance 52' rides along thesurface of the passive conductor strip, scrubs it and then reverses toseek a median position within the scrubbed area to insure excellentelectrical contact between the switch elements regardless of numerousswitching operations during vehicle use.

From the above description, it is apparent that open' cell foam stripsas at 34 and 40 in the first embodiment and 40' in the second embodimentact to electrically insulate the conductive strips from each other, andfurther provides the resilient means to force the primary lances todeflect to switch completion. 194 Olin (a trademark of the Olin MathesonCorporation) brass alloy forms the conductive strips from which thelances are partially struck out, the switch materials having goodelectrical conductivity, being generally noncorrosive and providingsuitable resilience to the lances. It should be noted that in the firstembodiment, the lances aid in moving the localized portion of the foamout of the area of protrusion as defined by the opening forming theindividual primary lances. In the second embodiment, the whole assemblyreverts to a flat planar position from the full line curved position,FIG. 11, once the occupant rises from the seat 10'.

The principles of the invention can be used for warning systems ofeither the front seat or the rear seat of a conventional sedan, assumingthat the front seat is capable of accomodating three passengers.

The foam strips 34, 40 are disclosed as being of the same material asthe upholstery foam in the interest of simplicity and convenience. Thesestrips can alternatively be of any suitable insulating material capableof undergoing resilient deformation since they function primarily asinsulating spacers. For example, they could be of molded plastic such aspolyethylene.

A distinct advantage of the provision of two secondary lances 52, 54 onthe primary lance 44 is that regardless of the loading and the amount offlexure of the primary lance, electrical contact between the primarylance and the passive strip will always be point contact between one orboth of the secondary lances and the passive strip. This result isachieved regardless of the extent to which the primary lance 44 isflexed and flatened against the passive strip by the load applied. Inthe absence of the second secondary lance, it is possible to flaten theprimary lance against the passive strip under extremely heavy loading sothat contact is established in a flatened contact area of the primarylance. If this type of contact is established, the unit pressure in thecontact area will drop so that a high resistance will de- '8 velop whichcan result in heating and deterioration of the switch.

It is understood that the term Mylar refers to po- Ilyethylene-terephthlate.

' vention.

What is claimed is:

1. A planar, low profile switch assembly operable by localizeddeformation by a human body sitting upon the same, said assemblycomprising:

an upper flexible, resilient electrically conductive metal strip,

a similar, lower, flexible, resilient, electrically conductive metalstrip,

a foam member interposed between said strips tending to maintain saidstrips in spaced, n0n-contact position in the absence of said humanbody,

at lease one primary lance partially struck from said upper strip andnormally lying in the same plane as the upper strip proper, but beingrelatively displaceable toward the other strip during forceabledepressible distortion of said assembly,

said foam member including an opening surrounding said primary lance topermit deflection of said lance within said foam member opening towardsthe strip and into contact therewith, 1

and said primary lance including at least one other short, secondarylance formed within the same and projecting downwardly therefrom in thesame direction as said primary lance deflection for initial contact withsaid lower metal strip.

2. The switch assembly as claimed in claim 1, wherein said secondarylances are two in number and are longitudinally spaced'from each otherand adjacent the free end of the primary lance, whereby, at least one ofsaid secondary lances moves longitudinally during contact with saidlower metal strip to effect a wiping action of the area of contact, andone of said secondary lances maintains contact with said lower metalstrip during intermittent movement of said other contact away from saidstrip to prevent arcing between said metal strips at the contactinterface.

3. The switch assembly as claimed in claim 1, wherein a second solidfoam member'overlies said upper metal strip, whereby compression of saidswitch assembly by said human body causes a localized portion of saidsecond foam member, corresponding to the opening in the upper stripdefined by the primary lance, to enter said opening and to depress theprimary lance into contact with the lower metal strip and upon bodyremoval, the resiliency of said primary lance forces the localizedportion of the second foam member back through the opening and returnsthe primary lance to a coplanar position with respect to said uppermetal strip.

4. The switch assembly as claimed a in claim 2, wherein a second solidfoam member overlies said metal strip, whereby compression by said bodyof said switch assembly causes a localized portion of said second foammember corresponding to the opening in the 9 upper strip defined by theprimary lance to enter said opening and depress the primary lance intocontact with the lower metal strip and upon body removal, the resiliencyof said primary lance forces the localized portion of the second foammember back through the opening and returns the primary lance to acoplanar I position with respect to said upper metal strip.

5. In combination, a seat construction including a pad of foam materialspanning the top of said seat, recesses within said foam pad at eachpossible occupant position, a planar lowprofile switch assembly carriedwithin each recess and operatively'responsive to local-v ized'occupancyofsaid seat,'each switch assembly comprising:

an upper flexible, resilient, electrically conductive metal strip, alower electrically conductive metal strip, a first foam strip interposedbetween said strips and tending to maintain said strips in spaced non-10' within said first foam strip opening into contact with said lowerstrip, and

a second unbroken foam strip overlying said upper metal strip,

whereby, occupancy of said seat at any one of said occupant positionscauses a localized portion of said second foam strip corresponding tothe opening in the upper metal strip to depress said primary lance intocontact with said lower metal strip.

6. The foam seat assembly as claimed in claim 5,

wherein said primary lance includes at least oneshort, secondary lancewithin said primary lance and project-f I ing'downwardly therefrom inthe same direction as said primary lance deflection to effect initialcontact with said lower metal strip. 7

7. The foam seat assembly asclaimed in claim 6, wherein said secondarylances are two in number and longitudinally spaced from each other andpositioned adjacent the free end of the primary lance and wherein saidprimary lance is struck out from said upper electrically conductivemetal strip in a direction such that at least one of said secondarylances makes wiping contact with said lower electrically conductivemetal strip during extending and retracing of said primary lance duringoccupancy so as to insure a clean electrical contact between said metalstrips. v

1. A planar, low profile switch assembly operable by localized deformation by a human body sitting upon the same, said assembly comprising: an upper flexible, resilient electrically conductive metal strip, a similar, lower, flexible, resilient, electrically conductive metal strip, a foam member interposed between said strips tending to maintain said strips in spaced, non-contact position in the absence of said human body, at lease one primary lance partially struck from said upper strip and normally lying in the same plane as the upper strip proper, but being relatively displaceable toward the other strip during forceable depressible distortion of said assembly, said foam member including an opening surrounding said primary lance to permit deflection of said lance within said foam member opening towards the strip and into contact therewith, and said primary lance including at least one other short, secondary lance formed within the same and projecting downwardly therefrom in the same direction as said primary lance deflection for initial contact with said lower metal strip.
 2. The switch assembly as claimed in claim 1, wherein said secondary lances are two in number and are longitudinally spaced from each other and adjacent the free end of the primary lance, whereby, at least one of said secondary lances moves longitudinally during contact with said lower metal strip to effect a wiping action of the area of contact, and one of said secondary lances maintains contact with said lower metal strip during intermittent movement of said other contact away from said strip to prevent arcing between said metal strips at the contact interface.
 3. The switch assembly as cLaimed in claim 1, wherein a second solid foam member overlies said upper metal strip, whereby compression of said switch assembly by said human body causes a localized portion of said second foam member, corresponding to the opening in the upper strip defined by the primary lance, to enter said opening and to depress the primary lance into contact with the lower metal strip and upon body removal, the resiliency of said primary lance forces the localized portion of the second foam member back through the opening and returns the primary lance to a coplanar position with respect to said upper metal strip.
 4. The switch assembly as claimed in claim 2, wherein a second solid foam member overlies said metal strip, whereby compression by said body of said switch assembly causes a localized portion of said second foam member corresponding to the opening in the upper strip defined by the primary lance to enter said opening and depress the primary lance into contact with the lower metal strip and upon body removal, the resiliency of said primary lance forces the localized portion of the second foam member back through the opening and returns the primary lance to a coplanar position with respect to said upper metal strip.
 5. In combination, a seat construction including a pad of foam material spanning the top of said seat, recesses within said foam pad at each possible occupant position, a planar low profile switch assembly carried within each recess and operatively responsive to localized occupancy of said seat, each switch assembly comprising: an upper flexible, resilient, electrically conductive metal strip, a lower electrically conductive metal strip, a first foam strip interposed between said strips and tending to maintain said strips in spaced non-electrical contact position, at least one primary lance partially struck from said upper strip and normally lying in the same plane as the upper strip proper, but being relatively displaceable during seat occupancy at a given position towards said lower strip, and an opening formed within said first foam strip surrounding the opening defined by said primary lance and permitting deflection of said primary lance within said first foam strip opening into contact with said lower strip, and a second unbroken foam strip overlying said upper metal strip, whereby, occupancy of said seat at any one of said occupant positions causes a localized portion of said second foam strip corresponding to the opening in the upper metal strip to depress said primary lance into contact with said lower metal strip.
 6. The foam seat assembly as claimed in claim 5, wherein said primary lance includes at least one short, secondary lance within said primary lance and projecting downwardly therefrom in the same direction as said primary lance deflection to effect initial contact with said lower metal strip.
 7. The foam seat assembly as claimed in claim 6, wherein said secondary lances are two in number and longitudinally spaced from each other and positioned adjacent the free end of the primary lance and wherein said primary lance is struck out from said upper electrically conductive metal strip in a direction such that at least one of said secondary lances makes wiping contact with said lower electrically conductive metal strip during extending and retracing of said primary lance during occupancy so as to insure a clean electrical contact between said metal strips. 